Herodotus seems to have traveled extensively around the ancient world, nearly all these territories were directly under the Persian Empire, conducting interviews and collecting stories for his book. At the beginning of The Histories, Herodotus sets out his reasons for writing it:

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This is the showing-forth of the inquiry of Herodotus of Halicarnassus, so that neither what has come to be from man in time might become faded, nor that great and wondrous deeds, those shown forth by Greeks and those by barbarians, might be without their glory; and together with all this, also through what cause they warred with each other.

^Herodotus (Book II, 68) claimed that the trochilus bird visited the crocodile, which opened its mouth in what would now be called a cleaning symbiosis to eat leeches. A modern survey of the evidence finds only occasional reports of sandpipers "removing leeches from the mouth and gular scutes and snapping at insects along the reptile's body."[4]